Field of the Invention
The present invention relates to a fuel cell stack.
Discussion of the Background
For example, a solid polymer type fuel cell has an electrolyte membrane and electrode structure (MEA) in which an anode electrode is arranged on one surface of the electrolyte membrane consisting of a polymer ion exchange membrane and a cathode electrode is arranged on the other surface thereof, respectively. In the electrolyte membrane and electrode structure, a power generating cell (unit cell) is constituted by being sandwiched between separators. Generally, the predetermined number of the power generating cells is stacked thereby to be loaded on a fuel cell powered vehicle for example as an onboard fuel cell stack.
In the fuel cell powered vehicle, there is a possibility that especially hydrogen of fuel gas leaks out in a space in which the fuel cell stack is loaded. Therefore, the fuel cell powered vehicle as disclosed in Japanese Patent Application Publication No. 2004-040950 is proposed on purpose to efficiently exhaust outwardly the hydrogen which leaks out of the fuel cell stack.
In this fuel cell powered vehicle, a closed space for loading the fuel cell thereon is arranged in front of a cabin. Then, as occasion demands, a first opening portion is provided in an upper part of the closed space and a second opening portion is provided in a position in which a negative pressure is generated at the time of travelling whereby to discharge the hydrogen leaking out from a fuel cell system into the closed space.
Accordingly, in the case where the opening portion is provided in the upper part of the closed space, the hydrogen leaking out from the fuel cell system within the closed space may be surely ventilated outside the vehicle especially in a stopping state of the vehicle. Moreover, in the case where the opening portion is provided in the negative pressure generating position, the hydrogen leaking out from the fuel cell system during travelling may be discharged from the closed space.